Green, by Laura Peyton Roberts (Delacorte, 2009, middle grade, 261pp).
When Lily was 12, she was an unremarkable, uncoordinated, socially uncertain middle-school kid, but when she turned 13, things changed with a bang. An exploding birthday present left on her front steps introduces her to the world of the leprechauns, and a trio of the little fellows whisks her off to the land of the Green Clan before she has a chance even to see how much of her hair she has left (it was a rather dramatic bang).
There in the Green she finds that she is expected to take the place of her beloved grandmother, who had died the year before--turns out her grandmother was the Keeper of the gold of Clan Green. But before Lily can become the Keeper herself, she must pass three tests...and she's not given any choice about the matter.
I have to confess, I was pretty skeptical about the whole leprechaun side of things. But that soon faded--Green is a fun and fast read that I enjoyed very much. Lily is not some specially gifted Chosen One; instead, she's smart, but only moderately determined, and not overly brave. The leprechauns also managed to avoid the pitfalls of Magical Creature Cliche, and were instead an interesting collection of individuals.
In short, this is a great one for middle school lover of fantasy who isn't ready for the dark complexity often found in books for older kids. I'd even go so far as to say, based on my own experience, that the grownup looking for something light and pleasant to read for themselves might well find this nicely diverting.
Here's another review at My Pile of Books.
(disclaimer: I received an ARC to review from the publishers at ALA)